1. Field of the Invention
With reference to the classification of art as established in and by the United States Patent and Trademark Office, the present invention is believed to be found in the general Class entitled, "Mining or in Situ Disintegration of Hard Material" (Class 229) and in the subclass entitled, "expansible breaking down devices--piston" (subclass 22) and the subclass of "forming blades" (subclass 15).
2. Description of the Prior Art
The use of a wedge and feathers to split rock and coal is well known. The forcing of a wedge between feather members to cause a side force to be developed has been shown in patents and apparatus for more than fifty years. The moving of a wedge member forwardly and backwardly by a hydraulic piston apparatus is also well known.
Nine U.S. Patents to H. Darda of Germany have employed a hydraulic cylinder to move a wedge between two held feathers. These patents include U.S. Pat. No. 3,414,328 as issued on Dec. 3, 1968; U.S. Pat. No. 3,439,954 as issued on April 22, 1969; U.S. Pat. No. 3,488,093 as issued on Jan. 6, 1970; U.S. Pat. No. 3,526,434 as issued on Sept. 1, 1970; U.S. Pat. No. 3,791,698 as issued on Feb. 12, 1974; U.S. Pat. No. 3,883,178 as issued on May 13, 1975; U.S. Pat. No. 3,894,772 as issued on July 15, 1975; U.S. Pat. No. 3,957,309 as issued on May 18, 1976, and U.S. Pat. No. 3,995,906 as issued on Dec. 7, 1976.
In these and other known rock splitting apparatus, the barrel is joined to an extension in which the piston rod is carried and in which the upper ends of the feathers are mounted in a sleeve member which is secured in a more-or-less permanent manner to the barrel. In these known arrangements, the retaining of the wedge is usually through an aperture in the side wall of this extension. In a like manner, the feathers are either brought in through the side of this extension or secured by pins engaged and retained in holes in this extension.
In the breaking of concrete and hard, large rocks, the DARDA apparatus Models 2, 2W, 3, 3W, 5, 5W and C-8 have been sold and are used in the United States as portable units which can be and are taken to a job for splitting rock and concrete. In these and other like apparatus damage does occur. Often this damage is to the wedge, feathers and/or to the wear plates which are used with the feathers in the rock splitting apparatus. Often this damage cannot be determined until and after damage has progressed beyond a repair point. Many repairs in addition to the wedge and feather replacement require a replacement of the lower barrel extension.
The basic concept and construction of the DARDA tool employs a hydraulic splitting cylinder which contains one plug and two feathers. This assembly is inserted into a pre-drilled hole with the plug in a retracted position. When the control lever is turned to forward position, the plug advances and the two feathers are forced sidewards against the wall of the hole and with hundreds of tons of pressure tears rock or concrete apart. With the control lever on top of the cylinder, the plug can be advanced, retracted or held in any position. A break usually occurs within 10 seconds but with extremely hard material, it could be up to 60 seconds.
In the use of the splitter, shown in U.S. Pat. No. 3,414,328, damage to the wedge, feathers and the piston guide member (No. 42 in FIG. 6) can occur when the operator moves or allows the tool to move sideward during splitting of the rock. Damage to the hardened rings or wear plates can also occur. In the splitter shown in U.S. Pat. No. 3,957,309, the screwed-in tubular element 56 of FIG. 5, the wear plates 64 and the wedge and feathers are very prone to damage. This apparatus, as used in commercial applications, is the DARDA Model No. 8 and is shown in FIGS. 5, 6 and 7 of U.S. Pat. No. 3,957,309. This wedge is pivotally secured at its upper end and the feathers are retained by springs 71. When rock of varying hardness is drilled and then split, it often results in a side movement of the wedge and feathers and a resulting damage to the wedge, feathers, housing 56 and the upper and lower wear plates 64 and 65. Replacement of the lower housing or shell requires a matching of the threaded end into the upper cylinder shell.
The present invention is directed toward a rock splitter in which the wedge and feathers are readily mounted and secured to provide inspection, replacement and repair. Instead of a lower tubular housing secured by a thread into the cylinder housing, there is provided a clam shell assembly which mounts into and onto exterior grooves formed in the cylinder barrel. As a repair or conversion for an existing DARDA splitting unit, the lower barrel portion is cut off and the grooves are formed in the remaining member portion. A clam shell retainer holds replaceable, throw-away wear washers, a wedge, a pair of feathers and a rubber retainer. These members are all held in place by a clamp strap. Ready removal of this clamp strap is contemplated so that inspection of the wear washers, the wedge, feathers and the clam shell retainers is easily made.